[FFmpeg-devel] [PATCH 1/2] avformat/dvbtxt: add raw demuxer for dvb teletext probing

[Marton Balint]

Signed-off-by: Marton Balint <cus at passwd.hu>
---
 libavformat/Makefile     |  1 +
 libavformat/allformats.c |  1 +
 libavformat/dvbtxt.c     | 50 ++++++++++++++++++++++++++++++++++++++++++++++++
 libavformat/utils.c      |  1 +
 libavutil/internal.h     | 15 +++++++++++++++
 5 files changed, 68 insertions(+)
 create mode 100644 libavformat/dvbtxt.c

diff --git a/libavformat/Makefile b/libavformat/Makefile
index 35a383d..38c6706 100644
--- a/libavformat/Makefile
+++ b/libavformat/Makefile
@@ -144,6 +144,7 @@ OBJS-$(CONFIG_DTS_MUXER)                 += rawenc.o
 OBJS-$(CONFIG_DV_DEMUXER)                += dv.o
 OBJS-$(CONFIG_DV_MUXER)                  += dvenc.o
 OBJS-$(CONFIG_DVBSUB_DEMUXER)            += dvbsub.o
+OBJS-$(CONFIG_DVBTXT_DEMUXER)            += dvbtxt.o
 OBJS-$(CONFIG_DXA_DEMUXER)               += dxa.o
 OBJS-$(CONFIG_EA_CDATA_DEMUXER)          += eacdata.o
 OBJS-$(CONFIG_EA_DEMUXER)                += electronicarts.o
diff --git a/libavformat/allformats.c b/libavformat/allformats.c
index 02bb16a..9662941 100644
--- a/libavformat/allformats.c
+++ b/libavformat/allformats.c
@@ -121,6 +121,7 @@ void av_register_all(void)
     REGISTER_DEMUXER (DTSHD,            dtshd);
     REGISTER_MUXDEMUX(DV,               dv);
     REGISTER_DEMUXER (DVBSUB,           dvbsub);
+    REGISTER_DEMUXER (DVBTXT,           dvbtxt);
     REGISTER_DEMUXER (DXA,              dxa);
     REGISTER_DEMUXER (EA,               ea);
     REGISTER_DEMUXER (EA_CDATA,         ea_cdata);
diff --git a/libavformat/dvbtxt.c b/libavformat/dvbtxt.c
new file mode 100644
index 0000000..5b0fafd
--- /dev/null
+++ b/libavformat/dvbtxt.c
@@ -0,0 +1,50 @@
+/*
+ * RAW dvb teletext demuxer
+ * Copyright (c) 2016 Marton Balnt <cus at passwd.hu>
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * FFmpeg is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "libavutil/internal.h"
+
+#include "avformat.h"
+#include "rawdec.h"
+
+static int dvbtxt_probe(AVProbeData *p)
+{
+    const uint8_t *end = p->buf + p->buf_size;
+    const uint8_t *buf;
+
+    /* The purpose of this is demuxer is to detect DVB teletext streams in
+     * mpegts, so we reject invalid buffer sizes */
+    if ((p->buf_size + 45) % 184 != 0)
+        return 0;
+
+    if (!ff_data_identifier_is_teletext(p->buf[0]))
+        return 0;
+
+    for (buf = p->buf + 1; buf < end; buf += 46) {
+        if (!ff_data_unit_id_is_teletext(buf[0]) && buf[0] != 0xff)
+            return 0;
+        if (buf[1] != 0x2c)     // data_unit_length
+            return 0;
+    }
+
+    return AVPROBE_SCORE_MAX / 2;
+}
+
+FF_DEF_RAWSUB_DEMUXER(dvbtxt, "dvbtxt", dvbtxt_probe, NULL, AV_CODEC_ID_DVB_TELETEXT, 0)
diff --git a/libavformat/utils.c b/libavformat/utils.c
index 129a49d..671a0c2 100644
--- a/libavformat/utils.c
+++ b/libavformat/utils.c
@@ -285,6 +285,7 @@ static int set_codec_from_probe_data(AVFormatContext *s, AVStream *st,
         { "ac3",       AV_CODEC_ID_AC3,        AVMEDIA_TYPE_AUDIO },
         { "dts",       AV_CODEC_ID_DTS,        AVMEDIA_TYPE_AUDIO },
         { "dvbsub",    AV_CODEC_ID_DVB_SUBTITLE,AVMEDIA_TYPE_SUBTITLE },
+        { "dvbtxt",    AV_CODEC_ID_DVB_TELETEXT,AVMEDIA_TYPE_SUBTITLE },
         { "eac3",      AV_CODEC_ID_EAC3,       AVMEDIA_TYPE_AUDIO },
         { "h264",      AV_CODEC_ID_H264,       AVMEDIA_TYPE_VIDEO },
         { "hevc",      AV_CODEC_ID_HEVC,       AVMEDIA_TYPE_VIDEO },
diff --git a/libavutil/internal.h b/libavutil/internal.h
index c4bcf37..ac8315d 100644
--- a/libavutil/internal.h
+++ b/libavutil/internal.h
@@ -338,4 +338,19 @@ void ff_check_pixfmt_descriptors(void);
 
 extern const uint8_t ff_reverse[256];
 
+/* Returns true if data identifier matches a teletext stream according to EN
+ * 301 775 section 4.4.2 */
+static av_always_inline int ff_data_identifier_is_teletext(int data_identifier)
+{
+    return (data_identifier >= 0x10 && data_identifier <= 0x1F ||
+            data_identifier >= 0x99 && data_identifier <= 0x9B);
+}
+
+/* Returns true if data unit id matches EBU teletext data according to
+ * EN 301 775 section 4.4.2 */
+static av_always_inline int ff_data_unit_id_is_teletext(int data_unit_id)
+{
+    return (data_unit_id == 0x02 || data_unit_id == 0x03);
+}
+
 #endif /* AVUTIL_INTERNAL_H */
-- 
2.6.2